The subject invention generally relates to a tandem vacuum booster assembly for a vehicle. More specifically, the subject invention relates to a tandem vacuum booster assembly that includes a sleeve disposed about a tie rod that to define an air passage such that air can be transferred between high pressure chambers of the assembly.
Tandem vacuum booster assemblies are known in the art. Tandem vacuum boosters assemblies are used in the braking systems of vehicles, in combination with a master cylinder, to boost brake performance such that the brakes of the vehicle operate with increased force.
Tandem vacuum booster assemblies include a front and rear housing that defines an interior chamber of the assembly. A divider is disposed between the rear housing and the front housing to partition the interior chamber into a primary chamber and a secondary chamber. These assemblies also include a primary diaphragm and a secondary diaphragm. The primary diaphragm is disposed between the rear housing and the divider to partition the primary chamber into two chambers, a primary high pressure chamber and a primary vacuum chamber. The secondary diaphragm is disposed between the divider and the front housing to partition the secondary chamber into two chambers, a secondary high pressure chamber and a secondary vacuum chamber. A tie rod, typically two tie rods, extends between the front and rear housings and also through the primary and secondary chambers to provide structural support to the assembly, especially to the primary and secondary diaphragms.
Tandem vacuum booster assemblies also include a push rod in mechanical connection with a piston in the master cylinder. The push rod is axially moveable by differential pressures that act upon the diaphragms. More specifically, when an operator of the vehicle applies the brakes, the push rod actuates a valve which permits air to enter the assembly on one side of the primary diaphragm, the high pressure side. This air increases pressure on that side of the diaphragm which causes the primary diaphragm to move and helps to push the push rod and actuate the piston in the master cylinder. In addition, air flows from the primary high pressure chamber to the secondary high pressure chamber to increase the pressure one side of the secondary diaphragm, the high pressure side. This pressure causes the secondary diaphragm to move which also helps to push the push rod and actuate the piston in the master cylinder.
In the prior art, there are several different mechanisms for transferring air between the high pressure chambers of the assembly. For example, tandem vacuum booster assemblies may include an air passage, or passages, through an outer bead of the primary diaphragm. Other conventional tandem vacuum booster assemblies channel air from the primary high pressure chamber to the secondary high pressure chamber through walls that surround the push rod. Tubes can also be utilized to transfer the air. The tubes utilized in the prior art are attached to either the rear housing or to the divider. The conventional mechanisms in which the air is transferred from the primary high pressure chamber to the secondary high pressure chamber are deficient because these mechanisms are typically costly, and it is difficult to assemble the components associated with these mechanisms. For example, some components require specific orientations relative to the tie rods and the push rod during assembly which can be overly cumbersome to an assembly operator.
Due to the inadequacies of the prior art, including those described above, it is desirable to provide a tandem vacuum booster assembly that provides for the transfer of air from the primary high pressure chamber to the secondary high pressure chamber, that is convenient to assemble, and that is economical to manufacture and assemble.
A tandem vacuum booster assembly for a vehicle is disclosed. The tandem vacuum booster assembly of the subject invention includes a rear housing and a front housing. The rear housing is adapted to be mounted to the vehicle, and the front housing is mounted to the rear housing to define an interior chamber. A divider is disposed between the rear housing and the front housing. The divider partitions the interior chamber into a primary chamber and a secondary chamber.
A primary diaphragm is disposed between the rear housing and the divider, and a secondary diaphragm is disposed between the divider and the front housing. The primary diaphragm partitions the primary chamber into a primary high pressure chamber and a primary vacuum chamber. The secondary diaphragm partitions the secondary chamber into a secondary high pressure chamber and a secondary vacuum chamber.
The assembly of the subject invention also includes a tie rod. The tie rod extends between the front and rear housings and also through the primary and secondary chambers. A sleeve is at least partially disposed about the tie rod and extends between the primary high pressure chamber and the secondary high pressure chamber. The sleeve is also at least partially spaced from the tie rod. As a result, the sleeve defines an air passage between the tie rod and itself such that air can be transferred between the high pressure chambers.
Accordingly, the subject invention provides a tandem vacuum booster assembly that provides for the transfer of air between the primary high pressure chamber and the secondary high pressure chamber. The sleeve included in the tandem vacuum booster assembly of the subject invention is conveniently assembled by simply slipping over the tie rod. Due to this convenient assembly, the costs associated with costs associated with assembling the tandem vacuum booster assembly of the subject invention are minimized.